US Bridges

Main ST over Mill Stream

Fair

Knox County, Maine · So End of Island · Structure no. 5711

Built
1959
66 years old
Condition
Fair
inspected December 2024
Type
Slab
Concrete
Length
46 ft
2 main spans
Daily traffic
4,273
2016 count
Owner
State
State Highway Agency

About this bridge

Main ST over Mill Stream is a concrete slab carrying Main ST over Mill Stream in Knox County, Maine. It was built in 1959, so it is 66 years old, older than the Maine average of 53.7 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 4,273 vehicles a day, roughly 5% of them trucks, projected to reach 5,982 by 2036. The structure is 46 ft (14.1 m) long and 45 ft wide. If it were closed, the detour would be 100 mi (161 km).

Location

Open in Google Maps
CarriesMain ST
CrossesMill Stream
LocationSo End of Island
RouteCounty Highway 0
CountyKnox County
StateMaine
Coordinates44.04749, -68.83425
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionDecember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating54.7 US tons
Inventory rating42.1 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans2
Design loadH 20
Structure length46 ft (14.1 m)
Longest span17 ft (5.3 m)
Deck width45 ft (13.7 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,273 (2016)
Projected traffic5,982 by 2036
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed100 mi (161 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was Main ST over Mill Stream built?

It was built in 1959, making it 66 years old in 2025.

What condition is Main ST over Mill Stream in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in December 2024.

How much traffic does Main ST over Mill Stream carry?

About 4,273 vehicles per day (2016 count), of which roughly 5% are trucks.

How long is Main ST over Mill Stream?

The structure is 46 ft (14.1 m) long with a longest span of 17 ft (5.3 m) and a deck 45 ft wide.

Who owns Main ST over Mill Stream?

It is owned by the State Highway Agency.